Obesity is a condition characterized in an increase in body fat content resulting in excess body weight above accepted norms. Obesity is the most important nutritional disorder in the western world and represents a major health problem in all industrialized countries. This disorder leads to increased mortality due to increased incidences of diseases such as cardiovascular disease, digestive disease, respiratory disease, cancer and NIDDM (type II diabetes). Searching for compounds, which reduce body weight has been going on for many decades. One line of research has been activation of serotonergic systems, either by direct activation of serotonin receptor subtypes or by inhibiting serotonin reuptake. The exact receptor subtype profile required is however not known.
Serotonin (5-hydroxytryptamine or 5-HT), a key transmitter of the peripheral and central nervous system, modulate a wide range of physiological and pathological functions, including anxiety, sleep regulation, aggression, feeding and depression. Multiple serotonin receptor subtypes have been identified and cloned. One of these, the 5-HT6 receptor, was cloned by several groups in 1993 (M Ruat, E Traiffort, J-M Arrang, J Tardivel-Lacombe, J Diaz, R Leurs, J-C Shwartz. Biochem. Biophys. Res. Commun. 1993, 193 (1) 268–276; M Sebben, H Ansanay, J Bockaert, A Dumuis, NeuroReport 5, 2553–2557 (1994).) This receptor is positively coupled to adenylyl cyclase and displays affinity for antipsychotics such as clozapine. Recently, the effect of 5-HT6 antagonist and 5-HT6 antisense oligonucleotides to reduce food intake in rats has been reported (J C Bentley, C A Mardsen, A J Sleight and K C Fone. Effect of 5-HT6 antagonist Ro 04-6790 on food consumption in rats trained to a fixed feeding regime. Br J Pharmacol. 1999 Suppl. 126, P66; J C Bentley, A J Sleight, C A Mardsen, K C F Fone. 5-HT6 antisense oligonucleotide ICV affects rat performance in the water maze and feeding. J Psychopharmacol Suppl A64, 1997, 255).
Compounds with enhanced affinity and selectivity for the 5-HT6 receptor have been identified, e.g. in WO 00/34242 and by M. Isaac, A. Slassi, T. Xin, N. MacLean, J. Wilson, K. McCallum, H. Wang and L. Demchyshyn: 6-Bicyclopiperazinyl-1-arylsulfonylindoles and 6-Bicyclopiperidinyl-1-arylsulfonylindoles derivatives as novel, potent and selective 5-HT6 receptor antagonists; Bioorganic & Medicinal Chemistry Letters 2000, 10, 1719–1721.